Single 550w panel to charge a 12v battery

[Hoocli]

Trying to run a couple small loads off grid on a 12v battery. I can get a 550w panel for pretty cheap so was hoping to set that up as direct sun / winter sun isn't great. Right now its using a super small panel and its not keeping it alive in the winter. Guessing maybe 20-50w. Going 550w is pretty overkill but the price is right.

I just need a solution that would allow me to charge a 12v battery using such a large panel. Just under 60v open. Initially I figured I could just throw w/e on it and overpanel abit hoping the controller wouldn't pull full load but I hear that's not a good idea. Atleast not with PWM.

Was trying to keep this project inexpensive yet reliable.

Will be fully exposed to rain/water. I can try to get it into some type of container but no guarantees on water ingress.

Figured this sub forum would be the most accurate place.

Hopefully someone here can give me some ideas. I could use a 100w panel but for double the price I can get a 550w. In the winter with crap sun I figured this was the better choice. Although haven't purchased yet so could be swayed.

 

[sunshine_eggo]

Most 12/24V PWM are limited to 50Voc. Furthermore, they force the panel to work at battery voltage, so your output will be Battery Voltage * panel Imp.

550W/14.4V = 38A, so to fully use the panel, you'll need an MPPT capable of 38A or higher. Lower will work, but you need to make sure it can handle the panel Voc and Isc in all conditions.

 

[Hoocli]

Most 12/24V PWM are limited to 50Voc. Furthermore, they force the panel to work at battery voltage, so your output will be Battery Voltage * panel Imp.

550W/14.4V = 38A, so to fully use the panel, you'll need an MPPT capable of 38A or higher. Lower will work, but you need to make sure it can handle the panel Voc and Isc in all conditions.

Thanks for the information. Ill keep considering and looking to see what there is.

 

[Rednecktek]

Pretty much any brand of real MPPT controller in the 40a+ range will do the trick. HQST, Vevor, RichSolar, even PowMr will turn solar DC into battery DC just fine. I would recommend a 50a if you can swing it but pretty much every real MPPT can handle that voltage and wattage just fine.

Pro Tip: If it's got USB ports on it, it's a FAKE controller with a MPPT sticker on it and someone is laughing at you all the way to the bank.

 

[sunshine_eggo]

Pretty much any brand of real MPPT controller in the 40a+ range will do the trick. HQST, Vevor, RichSolar, even PowMr will turn solar DC into battery DC just fine. I would recommend a 50a if you can swing it but pretty much every real MPPT can handle that voltage and wattage just fine.

Pro Tip: If it's got USB ports on it, it's a FAKE controller with a MPPT sticker on it and someone is laughing at you all the way to the bank.

You forgot Victron.

 

[Rednecktek]

You forgot Victron.

No, I really didn't. The day I recommend Victron equipment is the day I expect a concerted effort to find my body and whoever stole my identity.

And clear my browser history.

 

[Rocketman]

You will need a weatherproof box to put the charge controller into - none of the smaller residential grade ones (that I know about) are outdoor rated. And you may want that enclosure made from steel - so it will conduct heat away in the summer.

Personally I would go with the Victron Smart Solar 100/30 (or the 100/50) but there are a lot of options in this range.

One of the reasons I like Victron is the information you can get from it.

Here is a picture of the app (history page) from my 100/30 (420w of solar) -



(Had to go back a few days to get something interesting). The pieces I look at are the daily battery min and max and if the battery got into float

Some other options will be less expensive than a Victron 100/30- but it can handle the clipping of the 550w panel (I had 600w on my 100/30 for a while). And you can turn down the charging if you feel 30a is too much charge for your 100ah battery- ( I think that may be the case - but it’s been a while since I thought about the lead-acid max charge specs).

Good Luck with your decision.

 

[sunshine_eggo]

Smidgiest of smidges cheaper, has bluetooth and supports 48V as well.

But yeah... Victron sucks!

 

[Rednecktek]

You're going to want your SCC and inverter as close to the batteries as feasable to keep the fat wires short. Unless you're planning on keeping your batteries and inverter out in the weather...

 

[Rednecktek]

View attachment 235492

Smidgiest of smidges cheaper, has bluetooth and supports 48V as well.

But yeah... Victron sucks!

It gets a LOT more drastic of a difference when you go up in size. The 60a version is the equivalent of a 150/60, still has bluetooth, has a readable screen so you don't require an app to see if it's working, and is over $100 cheaper.

Screw $$Victron$$

Dear gods it's almost 3am and tonight is port day in Busan... frakking insomnia!!

 

[sunshine_eggo]

It gets a LOT more drastic of a difference when you go up in size. The 60a version is the equivalent of a 150/60, still has bluetooth, has a readable screen so you don't require an app to see if it's working, and is over $100 cheaper.

MAYBE I was selective...

Pfft... with Victron you don't need to see it's working. You know it is.

Screw $$Victron$$

Dear gods it's almost 3am and tonight is port day in Busan... frakking insomnia!!

DIY Solar forum is NOT a good cure for insomnia... at all. Go to bed!

 

[Hoocli]

You're going to want your SCC and inverter as close to the batteries as feasable to keep the fat wires short. Unless you're planning on keeping your batteries and inverter out in the weather...

That's the plan. Not sure if I'll need an inverter as both devices run off DC power. Might be able to direct tie to battery. 12v.

Any suggestions for a waterproof box? Especially for controller.

Could combine with battery or seperate. Need to keep the battery above freezing ideally. And would be nice to put it in the same box.

Considering throwing it into a hole in the ground as well.

This is going on the edge of the forest so trying to keep it waterproof and overkill enough to always work.

 

[Rednecktek]

Dead chest freezer on Craigslist? Got your insulation and weather seal all rolled into one.

 

[Rocketman]

Or an old (ice) cooler that still has.a good enough seal/lid. It will even have a drain in case any water gets in